1. Field of the Invention
The invention relates to an amorphous soft magnetic thin film which has a higher saturation magnetic flux density B.sub.s and a lower saturation magnetostriction constant .lambda..sub.s than films of the prior art.
2. Description of the Prior Art
In the field of magnetic recording, the tendency is towards increasing the density and the frequency of the recording signals, as evidenced by the newly developed perpendicular magnetic recording system. The magnetic media used in such recording systems consist of magnetic tapes having high residual magnetic flux density B.sub.r or high coercive force H.sub.c, composed of material such as evaporated metal magnetic tapes in which a ferromagnetic metal material is evaporated on a base film. The material of the magnetic head used in conjunction with the recording and/or reproduction of this type of magnetic recording medium must have a higher saturation flux density B.sub.s and a high magnetic permeability, and thus must be lower in its saturation magnetostriction constant .lambda..sub.s.
In systems utilizing high density magnetic recording, the recording track of the magnetic recording medium is usually reduced in width. Thus, the recording track of the magnetic head must also be reduced in width.
It has been suggested to provide a so-called composite magnetic head in which an insulating layer and a soft magnetic thin film adapted to serve as a magnetic core are alternately deposited on a non-magnetic base such as a ceramic. There has also been suggested a thin film magnetic head in which soft magnetic films and thin conductive films are arranged in a multilayer structure with intermediate insulating layers. For use as the soft magnetic thin film with such a type of magnetic head, soft amorphous magnetic films are attracting general attention.
The amorphous soft magnetic films are known to have a number of advantages such as a near-zero magnetostriction, a higher magnetic permeability, and freedom from crystal magnetic anisotropy, thus making them highly useful as a soft magnetic thin film for the aforementioned type of magnetic head.
The materials for constructing the amorphous soft magnetic thin film include metal-metalloid amorphous alloys in which the metalloid elements are contained in addition to the ferromagnetic metals such as Fe, Ni and Co. It is difficult, however, with the metal-metalloid amorphous alloys to produce a predetermined saturation magnetic flux density B.sub.s. For example, the .lambda..sub.s of the amorphous alloy becomes zero while its initial magnetic permeability along the difficultly magnetizable axis in the frequency range of 1 to 10 MHz is higher than about 3000. The alloys thus exhibit acceptable soft magnetic properties. However, in this case, the saturation magnetic flux density, B.sub.s, is lowered to less than about 14000 Gauss.
In summary, there has not been provided a soft magnetic thin film simultaneously satisfying the aforementioned requirements for saturation flux density B.sub.s and saturation magnetostriction constant .lambda..sub.s.
In our previous Japanese Patent Application No. 95320/1984 it was suggested to use a Co-Hf-Pt amorphous soft magnetic thin film wherein the saturation magnetic flux density B.sub.s was higher than 14000 Gauss and the saturation magnetostriction constant .lambda..sub.s was less than 1.5.times.10.sup.-6. However, with the above-described Co-Hf-Pt amorphous soft magnetic thin film, when it is desired to improve further the magnetic properties such as achieving a saturation flux density B.sub.s higher than 15000 Gauss and a saturation magnetostriction constant .lambda..sub.s less than 1.5.times.10.sup.-6, there exists only a narrow compositional range for which these two requirements are simultaneously satisfied.